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斜线和平面所成的角是高中《立体几何》教材中的重要内容,该角有一性质:斜线和平面所成的角,是这条斜线和平面内经过斜足的直线所成的一切角中最小的角.我们称该性质为最小角定理。如图,(1)AB⊥平面α,OB是斜线OA在α上的射影,∠AOB是OA和平面α所成的角,记∠AOB=θ1,过斜足O在α内任作一条直线OD,记∠BOD=θ2(θ2≤90°),∠AOD=θ3(θ3≤90°),在许多问题
The angle formed by slashes and planes is an important part of the high school “Three-Dimensional Geometry” textbook. The angle has one property: the angle formed by the slash and the plane is formed by this oblique line and a line passing through a diagonal foot in the plane. The smallest angle in all corners. We call this property the smallest angle theorem. As shown in the figure, (1) AB⊥ plane α, OB is the projection of the slash OA on α, ∠AOB is the angle formed by OA and plane α, and ∠AOB=θ1, the over-oblique foot O is made one in α. Straight line OD, note that BOD = θ2 (θ2 ≤ 90°), ∠ AOD = θ3 (θ3 ≤ 90°), in many problems